[v1] syztest | Patchew

syztest

Posted by Arnaud Lecomte 2 months, 1 week ago

#syz test

--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -5978,10 +5978,6 @@ struct mddev *md_alloc(dev_t dev, char *name)
 
 	disk->events |= DISK_EVENT_MEDIA_CHANGE;
 	mddev->gendisk = disk;
-	error = add_disk(disk);
-	if (error)
-		goto out_put_disk;
-
 	kobject_init(&mddev->kobj, &md_ktype);
 	error = kobject_add(&mddev->kobj, &disk_to_dev(disk)->kobj, "%s", "md");
 	if (error) {
@@ -5999,6 +5995,9 @@ struct mddev *md_alloc(dev_t dev, char *name)
 	kobject_uevent(&mddev->kobj, KOBJ_ADD);
 	mddev->sysfs_state = sysfs_get_dirent_safe(mddev->kobj.sd, "array_state");
 	mddev->sysfs_level = sysfs_get_dirent_safe(mddev->kobj.sd, "level");
+	error = add_disk(disk);
+	if (error)
+		goto out_put_disk;
 	mutex_unlock(&disks_mutex);
 	return mddev;
 
-- 
2.43.0

Re: [syzbot] [fuse?] [block?] KASAN: slab-use-after-free Read in disk_add_events

Posted by syzbot 2 months, 1 week ago

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+fa3a12519f0d3fd4ec16@syzkaller.appspotmail.com
Tested-by: syzbot+fa3a12519f0d3fd4ec16@syzkaller.appspotmail.com

Tested on:

commit:         4b290aae Merge tag 'sysctl-6.17-rc1' of git://git.kern..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10908834580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=295b41325f4e1bab
dashboard link: https://syzkaller.appspot.com/bug?extid=fa3a12519f0d3fd4ec16
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=15ac34a2580000

Note: testing is done by a robot and is best-effort only.

Re: syztest

Posted by Yu Kuai 2 months, 1 week ago

Hi,

在 2025/07/30 13:51, Arnaud Lecomte 写道:
> #syz test
> 
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -5978,10 +5978,6 @@ struct mddev *md_alloc(dev_t dev, char *name)
>   
>   	disk->events |= DISK_EVENT_MEDIA_CHANGE;
>   	mddev->gendisk = disk;
> -	error = add_disk(disk);
> -	if (error)
> -		goto out_put_disk;
> -
>   	kobject_init(&mddev->kobj, &md_ktype);
>   	error = kobject_add(&mddev->kobj, &disk_to_dev(disk)->kobj, "%s", "md");

This is wrong, you can't add mddev >kobj under the disk without
kobject_add for the disk kobj.

Thanks,
Kuai

>   	if (error) {
> @@ -5999,6 +5995,9 @@ struct mddev *md_alloc(dev_t dev, char *name)
>   	kobject_uevent(&mddev->kobj, KOBJ_ADD);
>   	mddev->sysfs_state = sysfs_get_dirent_safe(mddev->kobj.sd, "array_state");
>   	mddev->sysfs_level = sysfs_get_dirent_safe(mddev->kobj.sd, "level");
> +	error = add_disk(disk);
> +	if (error)
> +		goto out_put_disk;
>   	mutex_unlock(&disks_mutex);
>   	return mddev;
>   
>

Re: syztest

Posted by Arnaud Lecomte 2 months, 1 week ago

On 30/07/2025 07:09, Yu Kuai wrote:
> Hi,
>
> 在 2025/07/30 13:51, Arnaud Lecomte 写道:
>> #syz test
>>
>> --- a/drivers/md/md.c
>> +++ b/drivers/md/md.c
>> @@ -5978,10 +5978,6 @@ struct mddev *md_alloc(dev_t dev, char *name)
>>         disk->events |= DISK_EVENT_MEDIA_CHANGE;
>>       mddev->gendisk = disk;
>> -    error = add_disk(disk);
>> -    if (error)
>> -        goto out_put_disk;
>> -
>>       kobject_init(&mddev->kobj, &md_ktype);
>>       error = kobject_add(&mddev->kobj, &disk_to_dev(disk)->kobj, 
>> "%s", "md");
>
> This is wrong, you can't add mddev >kobj under the disk without
> kobject_add for the disk kobj.
>
Will dive a bit more into that after work,
Thanks

> Thanks,
> Kuai
>
>>       if (error) {
>> @@ -5999,6 +5995,9 @@ struct mddev *md_alloc(dev_t dev, char *name)
>>       kobject_uevent(&mddev->kobj, KOBJ_ADD);
>>       mddev->sysfs_state = sysfs_get_dirent_safe(mddev->kobj.sd, 
>> "array_state");
>>       mddev->sysfs_level = sysfs_get_dirent_safe(mddev->kobj.sd, 
>> "level");
>> +    error = add_disk(disk);
>> +    if (error)
>> +        goto out_put_disk;
>>       mutex_unlock(&disks_mutex);
>>       return mddev;
>>
>